The sigtrap pragma installs some simple signal handlers on your
behalf so that you don't have to worry about them. This is useful in
situations where an untrapped signal would cause your program to
misbehave, like when you have END {} blocks, object destructors, or
other at-exit processing that needs to be run no matter how your
program happens to terminate.

The sigtrap pragma provides two simple signal
handlers for your use. One provides a Perl stack trace, and the other
throws an ordinary exception via die. Alternately,
you can supply your own handler for the pragma to install. You may
specify predefined sets of signals to trap; you can also supply your
own explicit list of signals. The pragma can optionally install
handlers for only those signals that have not otherwise been handled.

Arguments passed to use sigtrap are processed in order. When a
user-supplied signal name or the name of one of sigtrap's
predefined signal lists is encountered, a handler is immediately
installed. When an option is encountered, this affects only those
handlers installed later in processing the argument list.

31.18.1. Signal Handlers

These options affect which handler will be used for
signals installed later:

stack-trace

This pragma-supplied handler outputs a Perl stack trace to STDERR
and then tries to dump core. This is the default signal handler.

YOURHANDLER will be used as the handler for
signals installed later. YOURHANDLER can
be any value valid for assignment into %SIG.
Remember that the proper functioning of many C library calls
(particularly standard I/O calls) cannot be guaranteed within a signal
handler. Worse, it's hard to guess which bits of C library code are
called from which bits of Perl code. (On the other hand, many of the
signals that sigtrap traps are pretty vile--they're
gonna take you down anyway, so there's not much harm in
trying to do something, now is there?)

31.18.2. Predefined Signal Lists

The sigtrap pragma has a few built-in lists of signals to trap:

normal-signals

These are the signals a program might normally expect to encounter,
and which, by default, cause it to terminate. They are the
HUP, INT, PIPE, and TERM signals.

error-signals

These are the signals that usually indicate a serious problem with
the Perl interpreter or with your program. They are the ABRT,
BUS, EMT, FPE, ILL, QUIT, SEGV, SYS,
and TRAP signals.

old-interface-signals

These are the signals that were trapped by default under an older
version of sigtrap's interface. They are ABRT, BUS,
EMT, FPE, ILL, PIPE, QUIT, SEGV,
SYS, TERM, and TRAP. If no signals or signals lists
are passed to use sigtrap, this list is used.

If your platform does not implement a particular signal named
in the predefined lists, that signal name will be silently ignored.
(The signal itself can't be ignored, because it doesn't exist.)

31.18.3. Other Arguments to sigtrap

untrapped

This token suppresses the installation of handlers for subsequently
listed signals if they're already been trapped or ignored.

any

This token installs handlers for all subsequently listed signals. This is the default behavior.

signal

Any argument that looks like a signal name (that is, one matching the
pattern /^[A-Z][A-Z0-9]*$/) requests sigtrap to handle
that signal.

number

A numeric argument requires the version number of the sigtrap
pragma to be at least number. This works is just like most regular
modules that have a $VERSION package variable:

% perl -Msigtrap -le 'print $sigtrap::VERSION'
1.02

31.18.4. Examples of sigtrap

Provide a stack trace for the old interface signals:

use sigtrap;

Same thing, but more explicitly:

use sigtrap qw(stack-trace old-interface-signals);

Provide a stack trace only on the four listed signals:

use sigtrap qw(BUS SEGV PIPE ABRT);

Die on an INT or a QUIT signal:

use sigtrap qw(die INT QUIT);

Die on any of HUP, INT, PIPE, or TERM:

use sigtrap qw(die normal-signals);

Die on HUP, INT, PIPE, or TERM--except don't change the behavior for
signals that have already been trapped or ignored elsewhere in the
program:

use sigtrap qw(die untrapped normal-signals);

Die on receipt of any currently untrapped normal-signals;
additionally, provide a stack backtrace on receipt of any of the
error-signals: